#!/usr/bin/env bash
#
# Generates sparklines for the next hour of precipitation in your current
# location. You can specify the number of minutes using the `-m` option. This
# relies on `whereami` (a Mac OS X utility), `jq`, and `spark`. Unfortunately,
# the proper version of Spark does not have support for the min/max flags that
# this utility needs, so you'll need to install a fork. Install everything using
# homebrew:
#
#   brew tap davidcelis/spark && brew install whereami jq davidcelis/spark/spark
#
# Additionally, you'll need to register a forecast.io API Key by visiting
# https://developer.forecast.io/ - once you've done that:
#
#   export FORECAST_API_KEY=my_api_key
#   forecast
#   ▅▇█▆▄▃▃▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁
#
#   forecast -m 15
#   ▅▇█▆▄▃▃▂▂▂▁▁▁▁▁
#
# The sparklines generated will be saved to /tmp/forecast.spark if you wish to
# easily access it from other utilities without repeating calls. Additionally,
# this utility will use that file's mtime to make sure that you do not go over
# the number of API requests that forecast.io gives you for free. As such, this
# utility will only attempt to call the forecast.io API if two minutes have
# passed since the last call.
sparkfile="/tmp/forecast.spark"
jsonfile="/tmp/forecast.json"
minutes=60

usage() { echo "Usage: forecast [-m <1...60>]" 1>&2; exit 1; }

while getopts ":m:" flag; do
  case "${flag}" in
    m)
      minutes=${OPTARG}
      ;;
    *)
      usage
      ;;
  esac
done
shift $((OPTIND-1))

if [ ! -f "$jsonfile" ]; then
  touch $jsonfile
  touch $sparkfile
fi

last=$(stat -f %m $jsonfile)
now=$(date +%s)

if (( ("$now" - "$last") > 120 )); then
  curl -Ss https://api.forecast.io/forecast/$FORECAST_API_KEY/$(whereami) > $jsonfile
  temperature=$(cat $jsonfile | jq ".currently.temperature" | xargs printf "%.0f")
  sparklines=$(cat $jsonfile |
                 jq ".minutely.data[:$minutes] | .[].precipIntensity * 10000" |
                 spark -m 0 -M 1500)

  echo $temperature"°F $sparklines" | tee $sparkfile
else
  cat $sparkfile
fi